Is Concrete or Cement Stronger Without Sand?
Cement is the most widely used construction material in the world, second only to water in terms of global demand. It is a versatile, relatively cheap substance that can be used to create extravagant and austere structures alike. There are many factors to consider when talking about the strength of concrete—some of which we’ll get into shortly—but one of the more common queries around this remarkable construction material is; is cement stronger without sand?
In the simplest terms, cement is not stronger without sand, but this answer would be leaving a lot of important information off of the table. For one thing, we need to establish whether we are talking about omitting sand from the ingredients that go into making cement itself, or whether we are talking about leaving sand out of the final mix for concrete—the product that is made using cement.
Cement Vs. Concrete
When we said cement was the most widely used construction material in the world, we were actually talking about concrete. That being said, you can’t make concrete without cement, and the two terms are often used interchangeably.
Cement is one of the ingredients that go into concrete, along with sand, water, and sometimes an aggregate. It is the sand and aggregate that forms the strength of the concrete. The cement is essentially little more than a very strong glue that holds everything together, and the proportions of those ingredients determine the properties of the final product.
If you were to add too much sand to your concrete mix, the final result would be “crumbly,” which is obviously less than ideal, particularly when building something structural. On the other hand, if you were to not put enough sand (or aggregate) into your mix, you would end up with concrete that is more watertight than a concrete mix with sand, but less strong.
The key to getting the desired strength of concrete is not the inclusion or omission of sand, but in getting the right proportion of sand.
Sand in Cement Vs. Sand with Cement
Sand is mixed with cement to make concrete, but it also features in the creation of cement itself—specifically silica sand. It should be noted that cement works thanks to chemical reactions that are a result of its component parts. Removing any of those parts is less a matter of whether it would be stronger, and more a matter of whether it would work as cement at all. For that reason, we are focussing on the inclusion of sand in the final concrete mix, rather than ingredients of cement itself.
What is the Best Ratio of Sand to Cement?
The first thing to note is that the ratio of your concrete’s ingredients will differ depending on the use case. The next thing to note is that the manufacturer of the cement you buy will usually give instructions for the correct ratios on the packaging, and you normally won’t go too far wrong by sticking to those instructions. Of course, we are assuming you are not a professional contractor or a large construction company where—we would assume you would not need this kind of advice if you were.
As a general rule, the ratio of ingredients in concrete would be;
- One part cement
- Two parts of sand
- Four parts aggregate
- Water added to desired consistency
For foundations, that mix may be tweaked to include three parts sand and six parts aggregate, but the basic proportions are there.
The Difference Between Concrete and Mortar
From a use-case standpoint, you could think of mortar as a macro-scale cement. It is used to glue together the bricks that make up a building in much the same way that cement acts to glue the aggregates of the concrete mix together. Conversely, concrete is used to make structures in their own right. So, rather than gluing the bricks together to make a wall, as mortar would, concrete would be used to make the entirety of the wall.
From an ingredients perspective, mortar does not have any aggregate in its mix. Mortar is not as strong as concrete, but that is because it is not designed to be structural, as such, but rather as an adhesive for other objects that are structural.
Why are Sand and Aggregates Necessary?
In addition to making the concrete stronger, as mentioned above, the sand and aggregates used in the concrete mix also serve an economic purpose. While concrete is one of the more affordable options for construction material, it still costs money to make. When you consider that the ratio we gave you above included seven parts in total, with only one of those parts being cement, you can probably appreciate how much money is saved by including aggregates and sand in the mix.
Of course, the process of acquiring sand and aggregates is not free, but it is certainly cheaper than the process of making cement, which involves heating the ingredients of cement to over two and a half thousand degrees Fahrenheit.
Does it Have to be Sand?
The truth is, there is no hard rule that states you have to use sand with cement in your concrete mix. That being said, there are a lot of compelling reasons to choose sand over something like crushed stone, and, ultimately, sand did not become a default ingredient for concrete without reason.
Once again, economics plays a large factor in sand’s inclusion in the concrete mix. It is possible to use crushed stone, but sand is more financially viable due to it being cheaper to obtain or manufacture. Another reason is its size; grains of sand are, as you probably know, very small.
The minuscule size of sand grains makes it possible to create a smooth concrete mix. If you were to use pebble-sized aggregate instead of sand, your concrete would be very bumpy. This would be fine for some situations, but most of the time, a finer consistency of concrete is preferred. It is also worth noting that even in concrete mixes that use a larger aggregate and have a rougher texture when cured, sand is still used to fill out the mixture.